A so-called throttle valve control device of an electronically-controlled throttle type, which in order to control the degree of opening of a throttle valve for a vehicle internal combustion engine, takes in or senses the amount of depression of an accelerator pedal as an electric signal by a detector (sensor), performs arithmetic processing on it, supplies the so-processed signal to an actuator comprised of a motor or the like and controls the opening and closing of the throttle valve by the actuator, is known in Japanese Patent Applicaticn Laid-Open No. 62-284932 or the like.
There has been a demand for a throttle valve control device allowing only this type of electronically-controlled throttle valve to perform all inclusive of air quantity control, such as ISC (Idle Speed Control), FIC (First Idle Control) in a region in which an intake air flow rate is less.
With a view toward allowing control of small or thin intake air quantity, it is necessary to allow the rate of change in air passage sectional area between the throttle valve and a wall surface of a intake pipe to finely vary with satisfactory accuracy according to a change in the degree of opening of the throttle valve as well as to improve the accuracy of control of the actuator itself to thereby permit fine control on the degree of opening of the throttle valve.
In regard to this point of view, as has been described in Japanese Patent Application Laid-Open Nos. 5-296067, 3-11133 and 3-15631 or Japanese Patent Application Laid-Open No. 56-56938 or the like, it is considered that some thought or ideas are put into profiles of a bore inner wall surface of an intake pipe opposed to a disc-shaped throttle valve, and the rate of changes in passage sectional area between the throttle valve and the wall surface with respect to a change in the degree of opening of the throttle valve is set so as to be able to be finely controlled in a low degree-of-opening region (FIC or ISC region) of the throttle valve.
An object of the present invention is to provide a novel throttle valve control device of capable of meeting the above-described demands on the electronically-controlled type throttle valve control device. However, this can be used when a like characteristic (e.g., generally called "delayed-opening characteristic") is required even in the case of a non-electronically-controlled type throttle valve control device.